A growth hormone called auxin.
By chemical photoreceptors A+LS :)
Hormones. answered via matering biology
One of the plant's hormones called auxins
plants grow towards light because of something called photo-tropism. this is why they will grow towards light. Search up Phototropism on Google!
Plants bend as they need light for photosynthesis. Its scientific term is phototropism.
Phototaxis
Plants in the dark receive no light and the plants need the light. They grow because the production of growth hormones is stimulated by the dark/suppressed by sunlight. This is why plants in the dark grow much more than plants in the light. (They will turn yellow because they are not receiving enough sunlight to produce chlorophyll to make the plant green. They will become unhealthy and eventually die.) It is also why plants in a sunny window "lean" toward the light. The side of the plant that is in the shade is producing more growth hormones.
Auxins which are plant hormones.
Tropism is the movement of a plant away from or toward a stimulus. The most easily found example of tropism is a plant's response to light. Plants tend to grow toward the light. This tendency is called 'phototropism'.
Thyroid hormones are made in the thyroid gland and are based on on the tyrosine amino acid composed of DNA base TAT or TAC. This gland usually secretes hormones which work toward Metabolism.
phototropism,
The moisture. Plants take the moisture out of humid air, especially if it hasn't rained in a while or they haven't been watered.